JPH05317846A - Diffusion treatment of water - Google Patents

Abstract

PURPOSE:To enable the simultaneous removal of the carbon dioxide and volatile org. halogen compd. incorporated into water contg. the carbon dioxide and volatile org. halogen compd. by treating the water in a spraying column. CONSTITUTION:The water contg. the carbon dioxide and the volatile org. halogen compd. is introduced, under an acidic condition, into a diffusion column 2 packed with a packing material to diffuse the carbon dioxide and the volatile org. halogen compd. The water is treated under the diffusion conditions of >=3m packing height of the packing material, <=50m/hour water passage rate and >=20Nm<3>/m<2> ventilation rate. As a result, the content of the volatile org. halogen compd. in the raw water which cannot be removed by an ion exchange treatment is drastically decreased and the treated water having high water quality is obtd. The carbon dioxide is removed as well together with the volatile org. halogen compd. in the diffusion column 2 and, therefore, the amt. of the caustic soda to be used for the purpose of regenerating the anion exchange resin of an anion exchange resin column 3 of a post-stage is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of dissipating water, and particularly to carbon dioxide gas suitable for a pure water production system requiring high purity such as PWR (pressurized water reactor) power generation water and semiconductor manufacturing water. And a method of simultaneously and efficiently removing carbon dioxide gas and a volatile organic halogen compound from water containing the volatile organic halogen compound in a diffusion tower.

[0002]

2. Description of the Related Art In recent years, pollution of river water and well water has progressed and PW
Raw water for producing pure water, which requires high purity such as R power generation water and semiconductor production water, often contains volatile organic halogen compounds such as trihalomethanes or precursors thereof.

On the other hand, the conventional PWR power generation water treatment apparatus is composed of a coagulation filtration tank, a two-bed three-column (or two-bed) deionizer, and a mixed-bed deionizer. Almost no volatile organohalogen compound in raw water can be removed.

Therefore, when raw water containing a volatile organic halogen compound flows in as raw water for such a PWR water treatment apparatus, the volatile organic halogen compound is directly supplied to the condensate system and taken into the steam generator. There is a problem in that halogen ions are generated by the decomposition of the volatile organic halogen compound under high temperature and high pressure, thereby increasing the corrosion of the steam generator.

When the raw water contains a precursor of a volatile organic halogen compound, the injection of sodium hypochlorite during coagulation filtration produces a volatile organic halogen compound, which is the same as above. Cause problems. Here, when the injection of sodium hypochlorite is stopped, the quality of filtered water is deteriorated and the amount of filtration treatment is significantly reduced, so the injection of sodium hypochlorite is essential.

On the other hand, conventional water treatment devices for semiconductor production include coagulation filtration tanks, reverse osmosis membrane devices, deionized water devices, and ultraviolet (U)
V) (Sterilizer) It consists of an oxidizer, an ion exchange resin tower, an ultrafiltration membrane device, etc., and although volatile organic halogen compounds are slightly removed by a UV oxidizer, most of it remains in the treated water. It will be done.

Therefore, when a volatile organic halogen compound is present in the raw water of such a semiconductor manufacturing water treatment apparatus,
The treated water, that is, the ultrapure water, does not have a low TOC (total organic matter concentration), which may reduce the yield of the obtained semiconductor products. Also, because of the halogen ions generated by the decomposition of the volatile organic halogen compound in the UV oxidizer,
There is also a problem that the ion load of the subsequent ion exchange resin tower is increased, the decrease of the ion exchange capacity is promoted, and the life thereof is shortened.

By the way, the volatile organic halogen compound is very volatile, and among the volatile organic halogen compounds, especially trichlorethylene may be removed by aeration treatment or diffusion tower treatment near neutral.

On the other hand, in the deionizer, a decarboxylation tower is often provided between the cation exchange resin tower and the anion exchange resin tower in order to reduce the amount of caustic soda used for regenerating the anion exchange resin. Also, in the reverse osmosis membrane device, since the removal rate of carbon dioxide gas is low, there is an example in which acid injection and decarboxylation are performed as pretreatment for improving the quality of treated water.

[0010]

Although the decarbonation tower adopts the same structure or principle as the desorption tower for the treatment of volatile organic halogen compounds, its gas-liquid ratio is significantly different, and the decarbonation tower is In, the volatile organohalogen compound is
Although it is very volatile in itself,
It remains almost without being removed. On the other hand, in a stripping tower for the purpose of removing volatile organic halogen compounds, most of the carbon dioxide gas in water exists as bicarbonate ions and carbonate ions. You cannot do it.

In view of the above conventional circumstances, the present invention removes the carbon dioxide gas and the volatile organic halogen compound contained at the same time by treating the water containing the carbon dioxide gas and the volatile organic halogen compound in the stripping tower. It is an object of the present invention to provide a method for dissipating water that enables the following.

[0012]

The method of water diffusion treatment according to the present invention comprises introducing water containing carbon dioxide gas and a volatile organic halogen compound into a diffusion tower filled with a filler under acidic conditions. A carbon dioxide gas and a volatile organic halogen compound are diffused. Preferably, as a diffusion condition, a filling height of the filler is 3 m or more and a water flow rate is 5
The treatment is performed at 0 m / hour or less and a ventilation rate of 20 Nm ³ / m ² / minute or more.

The present invention will be described in detail below. In the water diffusion method of the present invention, water containing carbon dioxide gas and a volatile organic halogen compound is acidified and then treated in a specific diffusion tower.

To make the water containing carbon dioxide gas and the volatile organic halogen compound acidic, an acid may be added,
Further, water may be passed through the cation exchange resin tower for ion exchange treatment, and the acidity thereof is preferably pH 4.8 or less. At pH of 4.8 or less, carbon dioxide does not dissociate into bicarbonate ions and the like.

In the present invention, if the filling height of the packing material of the stripping tower is 3 m or less, the efficiency of removing the volatile organic halogen compound together with carbon dioxide gas decreases. The packing height of this packing material is particularly preferably about 3 to 7 m, and in order to achieve such packing height, the height of the stripping tower is 5 to 10 m.
It is preferably m. Note that a net ring, Raschig ring, or the like can be used as the filler.

In the present invention, it is preferable to pass water in an acidic state to such a diffusion tower at a water flow rate of 50 m / hour or less and an aeration rate of 20 Nm ³ / m ² / min or more.

If the water flow rate exceeds 50 m / hour or the air flow rate is less than ²⁰ Nm ³ / m ² / minute, the efficiency of removing the volatile organic halogen compound together with carbon dioxide gas becomes poor. In addition, more preferable water flow and aeration conditions are water flow rate: 20 to 50 m / hour and air flow rate: 20 to 40 Nm ³ / m ² / minute.

[0018]

[Function] Water containing carbon dioxide and a volatile organic halogen compound is acidified and then introduced into a diffusion tower having a packing height of 3 m or more, and a water flow rate of 50 m / hour or less. Aeration rate: By treating at 20 Nm ³ / m ² / min or more, both carbon dioxide gas and the volatile organic halogen compound contained can be extremely efficiently diffused and removed.

Incidentally, the decarbonation tower, which is conventionally incorporated in the PWR water treatment apparatus and the semiconductor manufacturing water treatment apparatus, has a filling material filling height of about 1 m, and the water flow rate is 60 to 70 m / hour. The aeration rate is 10 m. It was ˜15 Nm ³ / m ² / min and it was possible to remove carbon dioxide gas, but it was difficult to remove volatile organic halogen compounds.

[0020]

Embodiments of the present invention will be specifically described below with reference to the drawings. 1 and 2 are system diagrams showing an example of an apparatus to which the method for dissipating water of the present invention is applied. FIG. 1 shows a water treatment apparatus for PWR power generation, and FIG. 2 shows a water treatment apparatus for semiconductor manufacturing.

The apparatus shown in FIG. 1 comprises a cation exchange resin tower 1, a diffusion tower 2, an anion exchange resin tower 3 and a mixed bed type ion exchange resin tower 4, and collects river water or well water or river water. Raw water obtained by filtration is introduced into a cation exchange resin tower 1 through a pipe 11, is subjected to a cation exchange treatment to be in an acidic state, and then introduced into a diffusion tower 2 through a pipe 12. In the stripping tower 2, the carbon dioxide gas and the volatile organic halogen compound contained in the stripping tower 2 are treated under the conditions of the present invention to be stripped and removed. The treated water in the stripping tower 2 is pump P
Is introduced into the anion exchange resin tower 3 from a pipe 13 provided with, and further introduced into the mixed bed type ion exchange resin tower 4 from a pipe 14 to be treated, and the treated water is discharged from a pipe 15.

In such a treatment apparatus, the volatile organohalogen compound in the raw water which cannot be removed by the ion exchange treatment is removed in the stripping tower 2, so that the content of the volatile organohalogen compound is remarkably reduced. , High quality treated water can be obtained. Further, since carbon dioxide gas is removed together with the volatile organic halogen compound in the stripping tower 2, the amount of caustic soda used for the regeneration of the anion exchange resin in the anion exchange resin tower 3 in the subsequent step can be reduced.

The apparatus shown in FIG. 2 comprises a stripping tower 5, a reverse osmosis membrane apparatus 6, a mixed bed type ion exchange resin tower 7, a UV oxidation apparatus 8, an ion exchange resin tower 9, and an ultrafiltration membrane apparatus 10. ,
The raw water is introduced into the stripping tower 5 through the pipe 21 after the acid such as H ₂ SO ₄ is injected through the pipe 21 to make the raw water acidic.
In the stripping tower 5, the treatment is carried out under the conditions of the present invention,
Both contained carbon dioxide gas and volatile organic halogen compounds are removed. The treated water in the stripping tower 5 includes a pipe 23 provided with a pump P, a reverse osmosis membrane device 6, a pipe 24, a mixed bed type ion exchange resin tower 7, a pipe 25, a UV oxidizer 8, a pipe 26, an ion exchange resin tower 9, The treated water is treated through the pipe 27 and the ultrafiltration membrane device 10, and the treated water is discharged from the pipe 28.

In such a treatment apparatus, the volatile organic halogen compounds in the raw water are removed together with carbon dioxide in the diffusion tower 5, so that decarboxylation as a pretreatment of the reverse osmosis membrane apparatus 6 and the ion exchange resin tower are carried out. Ion load reduction of 9, ie U
At the same time, the volatile organic halogen compound is removed in the stripping tower 5 in order to reduce the production amount of halogen ions in the V oxidation device 8.

The present invention will be described in more detail with reference to specific comparative examples and examples.

Comparative Example 1 1.5 ppm of sodium hypochlorite and 10 ppm of PAC (polyaluminum chloride) were poured into river water (content of volatile organic halogen compounds as shown in Table 1) and coagulated and filtered. The volatile organic halogen compounds in the filtered water were as shown in Table 1. The CO ₂ content (including bicarbonate ion and carbonate ion) was 8 to 10 ppm.

[0027]

[Table 1]

This coagulated filtered water was used as raw water to pass through a two-bed, three-column type deionizer and a mixed-bed type deionizer for treatment. The water flow conditions and device specifications are as shown in Table 2. Table 3 shows the volatile organic halogen compound and the CO ₂ content of the obtained treated water.

Example 1 In the method of Comparative Example 1, among the two-bed, three-column type deionizer,
The treatment was performed in the same manner except that the decarbonation tower was changed to a stripping tower, and the water flow conditions and device specifications were as shown in Table 2. Volatile organic halogen compounds and C of the obtained treated water
The O ₂ content is shown in Table 3. The effluent water of the cation exchange resin tower was under acidic conditions of pH 3.5 due to the cation exchange treatment.

[0030]

[Table 2]

[0031]

[Table 3]

From Table 3, it is clear that according to the method of the present invention, CO ₂ and volatile organic halogen compounds in the raw water can be efficiently diffused and removed at the same time. The treated water obtained in Comparative Example 1 and Example 1 was heat-treated in an autoclave at 275 ° C. for 1 hour and analyzed by an ion chromatography device. Was 10 ppb for chlorine ion and 5 ppb for bromine ion, whereas the treated water obtained in Example 1 had 1 ppb or less for both chlorine ion and bromine ion, and was confirmed to be extremely high purity. ..

[0033]

As described in detail above, according to the method for water diffusion treatment of the present invention, the carbon dioxide gas and the volatile organic halogen compound contained therein are diffused from the water containing the carbon dioxide gas and the volatile organic halogen compound. At the same time, it is possible to efficiently disperse and remove in the tower, and it is possible to obtain treated water of high water quality in which the carbon dioxide gas and volatile organic halogen compound contents are significantly reduced.

The method of the present invention as described above is applied to a treatment apparatus for PWR power generation water or semiconductor production water using river water, well water, etc. as raw water to obtain raw water contaminated with volatile organic halogen compounds and its raw water. Carbon dioxide gas of volatile organic halogen compounds in coagulated filtered water (such as raw water containing a precursor of volatile organic halogen compounds and sodium hypochlorite injected during coagulation filtration to produce volatile organic halogen compounds) It is possible to obtain the treated water of higher quality in the PWR power generation water treatment device, prevent halogen ions from increasing in the steam generator in the subsequent process, and suppress corrosion of the steam generator. In the semiconductor treatment water treatment apparatus, it is possible to obtain treated water having a lower TOC concentration and reduce the ion load of the ion exchange resin tower after the UV oxidation apparatus to extend its life. Such an effect is exhibited, which is extremely advantageous industrially.

[Brief description of drawings]

FIG. 1 is a system diagram showing a water treatment apparatus for PWR power generation to which a water diffusion treatment method of the present invention is applied.

FIG. 2 is a system diagram showing a semiconductor manufacturing water treatment apparatus to which the water diffusion treatment method of the present invention is applied.

[Explanation of symbols]

 1 Cation Exchange Resin Tower 2,5 Emission Tower 3 Anion Exchange Resin Tower 4,7 Mixed Bed Ion Exchange Resin Tower 6 Reverse Osmosis Membrane Device 8 UV Oxidation Device 9 Ion Exchange Resin Tower 10 Ultrafiltration Membrane Device

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C02F 1/58 HA 9/00 Z 7446-4D

Claims (1)

[Claims] 1. Water containing carbon dioxide and a volatile organic halogen compound is introduced into a stripping column filled with a filler under acidic conditions to diffuse carbon dioxide and the volatile organic halogen compound. A method of dissipating water.